| The Effect of Adrenaline on the Blockade of Compound Action Potential by Local Anesthetics in Rat Sciatic Nerves. |
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Yoon Choi, Joog Woo Leem, Hyun Cheol Yang, Jong Seok Yang, Sung Min Han, Jae Young Yu, Seung Woon Lim, Dong Myung Lee |
1Department of Anesthesiology, College of Medicine, University of Ulsan.
2Department of Physiology, College of Medicine, Yonsei University.
3Department of Anesthesiology, College of Medicine, Chungbuk National University. |
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| Abstract |
BACKGROUND
Adrenaline has often been used to prolong the local anesthetic effect during surgical procedures. As a possible explanation for this, a local vasoconstriction caused by adrenaline has been proposed. However, in a recent study, clonidine, an alpha2 adrenergic receptor agonist, was reported to block the conduction of mammalian nerves in vitro. Thus, there is a possibility that adrenaline may block nerve conduction by acting on the adrenergic receptor.
The present study is performed to see : (1) If adrenaline directly affects nerve conduction ; (2) If adrenaline affects conduction blockade caused by local anesthetic.
METHODS
Recordings of compound action potentials (CAPs) of A- and C-components were obtained from isolated sciatic nerves of adult male Sprague-Dawley rats. Dose-response curves of lidocaine and adrenaline regarding depression of CAPs were determined. Effects of adrenaline on the lidocaine-induced nerve block was assessed by comparing the effect of lidocaine (3.5x 10 5) with a lidocaine-epinephrine mixture (Lido-Epi, 3.5 x10 5 lidocaine with 1:100,000 epinephrine).
RESULTS
Adrenaline, near the clinical concentrations, had no effect on the size of either A- or C-component of CAPs.
The ED50 of lidocaine was 3.5x 10 5. Lidocaine depressed A-CAP 45.9+/- 7.0 when compared with baseline value, and the Lido-Epi solution depressed A-CAP to 41.7+/- 5.0 (P > 0.05).
Lidocaine depressed C-CAP 59.8 +/- 3.4 when compared with the baseline value, and the Lido-Epi solution depressed C-CAP to 60.5 8.1 (P > 0.05). Consequently, adrenaline did not augment lidocaine induced nerve blockade.
CONCLUSION
This study confirmed that adrenaline applied to the peripheral nerve has no effect either on nerve conduction itself or on conduction block produced by lidocaine. |
| Key Words:
Animals, rats; Local anesthetics, lidocaine; Monitoring, compound action potential; Nerve, sciatic; Pharmacology, adrenaline |
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